This invention relates to a color filter suitable for a combined use with liquid crystal or image sensor which can be used in television, video monitor or display and image scanner of computer. In the color liquid crystal display devices of prior art containing a liquid crystal and a color filter as its constitutional elements for controlling transmission or reflection of light, the color filter has been prepared by forming red-, green- and blue-colored image elements and black matrix on a glass substrate by the dyeing process or printing process. Particularly in color liquid crystal display devices requiring an image of high precision, a color filter prepared by dyeing process is mainly used. Color image scanner is also in the same situation as above. However, prior color filters have been disadvantageous in the following point.
Thus, a color filter prepared by dyeing process is prepared by using a natural photosensitive components such as gelatine and the like or a synthetic photosensitive resin such as amine-modified polyvinyl alcohol and the like as a dyeing substrate and dyeing it with a dye such as acid dye and the like. However, this type of color filter is disadvantageous in that it is poor in reliabilities such as light resistance, heat resistance and moisture resistance. On the other hand, prior color filter prepared by printing process were prepared by the use of an ink formed by dispersing a pigment into a thermosetting resin or an ultravioletcurable resin. However, this type of color filter is inferior in the ability to give a pattern of high precision and in surface smoothness. Although an ink prepared by dispersing a pigment into a photosensitive polyimide resin is disclosed in Japanese Patent Application Kokai (Laid-Open) No. 60-237,403, polyimide resin is disadvantageous in that, if its thickness exceeds 1.0 micron, an absorption appears in the visible region and color reproducibility is deteriorated. Particularly when electrical field strength and light path length of cell gap must be varied by changing the thicknesses of red, green and blue image elements for the purpose of improving contrast (hereinafter, this procedure is simply referred to as "multi-gap"), it is difficult to achieve a color reproducibility comparable to that of CRT.
As photopolymerization initiator of photosensitive resins, polycyclic quinone compounds such as anthraquinone, naphthoquinone and the like have hitherto been used. However, there has been a practical problem that they are so low in sensitivity that formation of image element upon irradiation with light takes a long period of time particularly when the photosensitive resin contains a pigment.
Further, if pigment concentration is elevated in order to achieve a good color reproducibility, no sufficient polymer can be obtained by irradiation with light only, so that the resin is not good in adhesive property and cannot form a fine image upon development. Further, there has been a problem in the point of environmental reliability, too. Apart from the above, a product prepared by dispersing a pigment into a natural photosensitive component or photosensitive polyvinyl alcohol resin may also be thought out. However, this type of product is not good in resolving power, sensitivity and dispersion stability. Further, it is poor in heat resistance and moisture resistance.
The next problem is that, if a pigment is dispersed as it is, it cannot be finely dispersed because of coagulation and association and, if it can once be dispersed, the resulting dispersion is not stable because re-agglomeration takes place. Next, in the electrode structure of color filter, if a transparent electrode such as ITO and the like is provided on a transparent substrate made of glass or the like and a color filter is constructed thereon, the insulating layer causes a drop in voltage so that a higher voltage must be applied to the panel in order to achieve the desired liquid crystal panel characteristics. Particularly in case of multi-gap panel, this makes it impossible to apply voltage in accordance with the kind of image element (red, green and blue). Further, when a TFT element composed of amorphous silicon is used, light must be intercepted, and hence the concentration of pigment such as carbon black in the black matrix must be enhanced which brings about a problem that the voltage in the considered area becomes different from that in other image elements.